1. Field of the Invention
The invention relates to the transfer of electric energy to a vehicle, in particular to a track bound vehicle such as a light rail vehicle (e.g. a tram) or to a road automobile such as a bus or a private automobile. A corresponding system comprises an electric conductor arrangement for producing an alternating electromagnetic field and for thereby transferring electromagnetic energy to the vehicle. The conductor arrangement comprises a plurality of segments, wherein each segment extends along a different section of the path of travel (track) of the vehicle. The invention also relates to a corresponding method of manufacturing the system and to a corresponding method of operating the system.
2. Description of Related Art
Track bound vehicles, such as conventional rail vehicles, mono-rail vehicles, trolley busses and vehicles which are guided on a track by other means, such as other mechanical means, magnetic means, electronic means and/or optical means, require electric energy for propulsion on the track and for operating auxiliary systems, which do not produce traction of the vehicle. Such auxiliary systems are, for example, lighting systems, heating and/or air condition system, the air ventilation and passenger information systems. However, more particularly speaking, the present invention is related to a system for transferring electric energy to a vehicle which is not necessarily (but preferably) a track bound vehicle. A vehicle other than a track bound vehicle is a bus, for example. An application area of the invention is the transfer of energy to vehicles for public transport. Generally speaking, the vehicle may be, for example, a vehicle having an electrically operated propulsion motor. The vehicle may also be a vehicle having a hybrid propulsion system, e.g. a system which can be operated by electric energy or by other energy, such as electrochemically stored energy or fuel (e.g. natural gas, gasoline or petrol).
WO 2010/031593 A1 describes a system and a method for transferring electric energy to a vehicle, wherein the system comprises the features mentioned above. It is disclosed that the system comprises an electric conductor arrangement for producing an alternating electromagnetic field and for thereby transferring the energy to the vehicle. The electric conductor arrangement comprises at least two lines, wherein each line is adapted to carry a different one of phases of an alternating electric current. The conductor arrangement comprises a plurality of segments, wherein each segment extends along a different section of the path of travel of the vehicle. Each segment comprises sections of the at least two lines and each segment can be switched on and off separately of the other segments. Each one of successive segments of the conductor arrangement can be connected via a separate switch for switching on and off the element to a mainline.
WO 2010/000495 A1 describes the field of invention and possible embodiments of the conductor arrangement in more detail. In particular, the serpentine-like embodiment of the conductor arrangement can also be chosen for the present invention.
Each segment may be connected to a direct current supply via an inverter for converting the direct current to an alternating current for producing the electromagnetic field. Alternatively, the segments may be connected to an alternating current supply, for example via an AC/AC voltage converter. Combinations are possible, for example two segments may be connected to a direct current supply via a common inverter.
US 2003/0200025 A1 discloses a roadway-powered electric vehicle system comprising a network of roadways electrified with a multiplicity of roadway power transmitting modules embedded in the roadways at selected locations, each of said roadway power transmitting modules being connected to receive power from an electrical utility. The document also discloses that the roadway power transmitting modules can be grouped in clusters of five modules with each cluster being powered from the same power conditioner. The clusters are spaced along the length of the roadway with a non-electrified section of roadway separating the clustered sections. Therefore, neighboring modules of a cluster are powered from the same power conditioner. To provide a continuous power transfer to an electric vehicle, however, the power conditioner needs to power more than one module at a time or to switch between the respective modules of the cluster. Operating more than one module at a time disadvantageously can reduce the power transferred to the operated modules and/or can disadvantageously change desired parameters, e.g. a nominal value or rms-value of an operating alternating current, of the power supply. Switching between the modules can also disadvantageously alter the quality of power supply to an electric vehicle, e.g. in case multiple segments need to be powered to provide sufficient power to the vehicle. This is e.g. the case if a vehicle, e.g. a rail vehicles or a trolley bus, comprises more than one receiver and covers more than one segment such that power needs to be transmitted by closely spaced segments, e.g. neighboring segments.
In order to transfer sufficient power for providing vehicles (in particular trams or busses) for propulsion, currents of at least some tens of Amperes and voltages of at least some tens of Volts are required, i.e. the transferred power should be in the range of at least some kW. In case of a tram, for example, the voltage at the segment may be in the range of 500-1.000 V and the effective current through the segment may be in the range of 150-250 A.
Corresponding impedances, in particular inductances, require heavy components having corresponding large volumes. In addition, these components produce a significant part of the costs of manufacturing such a system.